The Vatican was accused of orchestrating a cover-up over the disgraced Scottish Cardinal Keith O'Brien amid claims that it knew of allegations against him for five months but kept them secret.

Revelations that the most senior Roman Catholic cleric in Britain had a secret sex life cast a shadow over the first day of a meeting of the church's cardinals as they gathered to choose a successor to Benedict XVI, now Pope Emeritus.

The 142 'princes of the church' met in the Paul VI Hall of the Vatican to discuss the church's problems and the sort of qualities required of the new Pope to deal with them.

But officials in Rome and the Vatican's representative to Britain flatly refused to discuss how long Benedict XVI had known about the accusations against Cardinal O'Brien, pictured above, or how many accusers there are.

After denying that he had made sexual advances to four men – three priests and one former priest – Cardinal O'Brien issued a statement on Sunday confessing that his "sexual conduct" had fallen far below the standard expected. It came a week after he stepped down as Archbishop of St Andrews & Edinburgh and announced that he would stay away from the conclave.

Claims emerged yesterday that a fifth priest had come forward as early as October last year, sending a complaint directly to the Vatican about alleged approaches by Cardinal O'Brien.

The Vatican has said that the British cardinal tendered his resignation around November last year, in anticipation of turning 75 this month.

That prompted speculation that the Vatican negotiated a deal months ago in which the British cardinal would retire quietly in an attempt to spare embarrassing the church.

It has been alleged that the deal was brokered by Cardinal Marc Ouellet of Canada, one of the front-runners to be elected Pope.

Vatican spokesmen refused to answer questions about whether an official investigation had been opened into the scandal.

Vatican officials would not say whether any disciplinary action would be taken.

An association of victims of sex abuse by clergy said there were many cardinals who had covered up sexual abuse by priests. "It might sound extreme but we suspect most of the cardinals to be complicit in covering up predator priests.

"Crises have erupted in country after country and the pattern is always the same," David Clohessy of Survivors Network of those Abused by Priests, said.